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P-2 Electrocrystallization of Calcium Phosphates for Orthopaedic Implants
Journal of Biomechanics 43S1 (2010) S3–S14
Contents lists available at ScienceDirect
Journal of Biomechanics journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com
Plenary Lectures P-1 Hip Resurfacing: The Past, the Present and the Future A. Moroni. Bologna University, Rizzoli Orthopaedic Institute, Italy 1951 saw the first hip resurfacing (HR) procedure performed by Sir John Charnley using teflon-on-teflon bearings [1]. Approximately 20 years later, a polyethylene acetabular component and metal femoral component had become popular but osteolysis was prevalent due to tissue response to wear particles [2,3]. By the early 1980s, HR had almost been phased out due to high failure rates, but work continued in some centres, leading to the development of metal-on-metal (MOM) HR prostheses. The advantages of using MOM components in HR include less wear and bone re-absorption, and a low rate of dislocation [4]. Indeed, various reports in the literature have documented excellent short and mid-term results and low complication rates associated with MOM HR [5–7]. The results of our series of over 1000 patients treated with MOM HR are in agreement with such reports. The mean patient age at the time of surgery was 53.8 years (range 16 to 82). The mean Harris hip score (HHS) was 98 points at a mean follow-up of 2 years. The following major complications were recorded: 9 femoral neck fractures (FNFs), 2 acetabular component loosenings, 1 pseudotumour and 1 sciatic peroneal nerve deficit. Although we believe that MOM HR is a successful technique, long-term studies have not yet been published and there is always room for improvement. MOM implants do in fact have several drawbacks, including osteolysis, implant loosening, the development of hypersensitivity and pseudotumours [8–10], and serum metal ion elevation [11], the latter being particularly important with regards to fertile females. A novel type of bearing for use in HR consists of an uncemented 2.7 mm-thick acetabular polycarbonate-urethane (PCU) component, which can be coupled to large diameter metal heads. Commercially known as the Tribofit® Acetabular Buffer™ (Active Implants Corporation, Memphis Tennessee, USA), this innovative bearing allows fluid film lubrication and as a result, wear is minimized. PCU is a hydrophilic, biocompatible, endotoxin-resistant material and acts as a stress-absorber, transmitting loads to the subchondral bone in a physiological manner. As of January 2010, 3 patients with avascular necrosis (AVN) and 5 with osteoarthritis (OA) were treated with HR using the Buffer™. Large diameter cobalt-chromium (CoCr) resurfacing heads were used in all patients (Tribofit® , Active Implants Corporation, Memphis, Tennessee, USA). The mean patient age at the time of surgery was 53.1 years (range 30 to 68). In pristine sockets, no acetabular bone reaming was performed and the Buffer™ alone was used. In 3 of the OA patients who had deformed sockets, standard reaming was performed and the Buffer™ was placed into an acetabular metal shell, the former acting as a liner. The mean follow-up in this patient series was 12 months (range 0 to 25). No osteolysis or loosening were observed on X-rays. However, in 1 patient who did not have the acetabular metal shell, the acetabular bone had been mistakenly reamed. The patient became symptomatic 2 years after surgery and periacetabular bone 0021-9290/$ – see front matter © 2010 Elsevier Ltd. All rights reserved.
rarefaction was visible. The mean HHS of the remaining cases at the latest follow-up was 99. In conclusion, HR has gone a long way since its development over 50 years ago. MOM HR is a successful technique performed worldwide, but implant longevity and the long-term effects of wear debris remain unclear. However, with the continuous evolution of hip bearings and the recent developments in technology, HR is set to be taken to the next level. Reference(s) [1] Charnley JC. Arthroplasty of the hip: a new operation. Lancet I, 1961; 1129–1132. [2] Amstutz HC, Graff-Radford A, Gruen TA, Clarke IC. THARIES surface replacements: a review of the first 100 cases. Clin Orthop Relat Res. 1978; 134:87–101. [3] Howie DW, Campbell D, McGee M, Cornish BL. Wagner resurfacing hip arthroplasty. The results of one hundred consecutive arthroplasties after eight to ten years. J Bone Joint Surg Am. 1990; 72(5):708–714. [4] K.A. De Smet, C. Pattyn, R. Verdonck. Early results of primary Birmingham hip resurfacing using a hybrid metal-on-metal couple. Ghent University Hospital, Ghent, Belgium. Hip International 2002; 12(2):158–162. [5] Daniel J, Pynsent PB, McMinn DJ. Metal-on-metal resurfacing of the hip in patients under the age of 55 years with osteoarthritis. J Bone Joint Surg Br. 2004; 86(2):177–184. [6] Treacy RB, McBryde CW, Pynsent PB. Birmingham hip resurfacing arthroplasty. A minimum follow-up of five years. J Bone Joint Surg Br. 2005; 87(2):167–170. [7] Amstutz HC, Beaule´ PE, Dorey FJ, Le Duff MJ, Campbell PA, Gruen TA. Metal-on-metal hybrid surface arthroplasty: two to six-year follow-up study. J Bone Joint Surg Am. 2004; 86-A(1):28–39. [8] Park Y-S, Moon Y-W, Lim S-J, Yang J-M, Ahn G, Choi Y-L. Early osteolysis following second-generation metal-on-metal hip replacement. J Bone Joint Surg Am. 2005; 87:1515–1521. [9] Willert H-G, Buchhorn GH, Fayyazi A, Flury R, Windler M, Koster G, Lohmann CH. Metal-on-metal bearings and hypersensitivity in patients with artificial hip joints. A clinical and histomorphological study. J Bone Joint Surg Am. 2005; 87:28–36. [10] Pandit H, Glyn-Jones S, McLardy-Smith P, Gundle R, Whitwell D, Gibbons CL, Ostlere S, Athanasou N, Gill HS, Murray DW. Pseudotumours associated with metal-on-metal hip resurfacings. J Bone Joint Surg Br. 2008; 90(7):847–851. [11] Clarke MT, Lee PTH, Arora A, Villar RN. Levels of metal ions after small and large diameter metal-on-metal hip arthroplasty. JBJS 2003; 85B6:913–917.
P-2 Electrocrystallization of Calcium Phosphates for Orthopaedic Implants N. Eliaz. Tel-Aviv University, Israel Apatite is the primary inorganic constituent of all mammalian skeletal and dental tissues. It belongs to the family of calcium phosphates (CaP), which includes, among others, hydroxyapatite (HAp, Ca5 (PO4 )3 (OH)) and octacalcium phosphate (OCP, Ca4 (HPO4 )(PO4 )2 ·2.5H2 O). In their synthetic form, apatites are typically bioactive ceramics, which are more osteoconductive than
S4
Plenary Lectures / Journal of Biomechanics 43S1 (2010) S3–S14
metal surfaces and form direct bonds with adjacent hard tissues via dissolution and ion exchange with body fluids. Hence, several types of synthetic apatites are now commercially available for use in bone repair, bone augmentation, bone substitution, and as coatings on orthopaedic and dental implants. Several methods have been explored to deposit CaP coatings in order to enhance implant fixation. Plasma spraying is the most common technology used commercially. Since the early 1990’s, however, much interest in electrodeposition has evolved. In recent years, our group has been studying different aspects related to electrocrystallization (i.e. the nucleation and crystal growth in electrochemical systems under the influence of an electric field) of HAp and other calcium phosphates. Some of these aspects will be presented in this talk. Electrocrystallization was achieved potentiostatically in solutions containing calcium nitrate and ammonium dihydrogen phosphate at an initial pH of either 4.2 (HAp4.2) or 6.0 (HAp6.0). Both the surface texture and the contact angle of the ground titanium substrate changed as a result of either heat treatment following soaking in NaOH solution or soaking in H2 O2 solution [1,2]. Consequently, the shape of the current transients during potentiostatic deposition of HAp changed, and the resulting coatings exhibited different surface textures and contact angles. Pure, highly crystalline HAp could be deposited on CP-Ti and Ti-6Al-4V [3–6]. The HAp4.2 coatings were thicker, less crystallized and more porous than HAp6.0 coatings, and revealed traces of OCP as well as a different surface morphology [5]. Bath temperature played an important role in the formation of the stoichiometric HAp coating. The synthetic HAp exhibited a hetero-epitaxial-like behaviour on Ti substrates, similar to the biological apatite [7]. The deposition changed from instantaneous nucleation/2D growth to progressive nucleation/3D growth [7,8]. The corrosion resistance of HAp6.0 coatings was better than that of HAp4.2 coatings [5]. The solubility of the CaP affected the kinetics of bone ingrowth significantly [9]. The use of Ra and Z rms might lead to misleading conclusions, particularly when studying porous coatings such as HAp. The use of the S dr was found more sensitive and reliable in distinguishing between different surfaces and predicting their effect on cell attachment [1]. The higher content of OCP in NaOH-ED-HAp, as evident from X-ray photoelectron spectroscopy (XPS) analysis of the oxygen shake-up peaks, and the associated increase in the solubility of this coating in vivo may be responsible for the enhanced osseointegration [8,10]. Evaluation of the shape and coverage of MBA-15 cells in vitro showed that the HAp6.0 coatings provided enhanced cell response [1]. It is concluded that electrochemical deposition of HAp following soaking in NaOH may become attractive, both industrially and clinically, for coating cementless implants used for joint reconstruction. Reference(s) [1] N. Eliaz, S. Shmueli, I. Shur, D. Benayahu, D. Aronov and G. Rosenman, The effect of surface treatment on the surface texture and contact angle of electrochemically deposited hydroxyapatite coating and on its interaction with bone-forming cells, Acta Biomater. 5 (2009) 3178– 3191. [2] O. Ritman, The effect of surface treatments on the interaction of HAp-coated titanium with cells and bacteria, M.Sc. Thesis, Tel-Aviv University, Israel (2008). [3] T.M. Sridhar, N. Eliaz, U. Kamachi Mudali and Baldev Raj, Electrophoretic deposition of hydroxyapatite coatings and corrosion aspects of metallic implants, Corros. Rev. 20(4–5) (2002) 255–293. [4] N. Eliaz, T.M. Sridhar, U. Kamachi Mudali and Baldev Raj, Electrochemical and electrophoretic deposition of hydroxyapatite for orthopaedic applications, Surf. Eng. 21(3) (2005) 238–242. [5] N. Eliaz and T.M. Sridhar, Electrocrystallization of hydroxyapatite and its dependence on solution conditions, Cryst. Growth Des. 8(11) (2008) 3965–3977. [6] N. Eliaz, Electrocrystallization of calcium phosphates, Israel J. Chem. 48(3/4) (2008) 159–168.
[7] N. Eliaz and M. Eliyahu, Electrochemical processes of nucleation and growth of hydroxyapatite on titanium supported by real-time electrochemical atomic force microscopy, J. Biomed. Mater. Res. A 80(3) (2007) 621–634. [8] N. Eliaz, W. Kopelovitch, L. Burstein, E. Kobayashi and T. Hanawa, Electrochemical processes of nucleation and growth of calcium phosphate on titanium supported by real-time quartz crystal microbalance measurements and XPS analysis, J. Biomed. Mater. Res. A 89(1) (2009) 270–280. [9] H. Wang, N. Eliaz, Z. Xiang, H.-P. Hsu, M. Spector and L.W. Hobbs, Early bone apposition in vivo on plasma-sprayed and electrochemically deposited hydroxyapatite coatings on titanium alloy, Biomaterials 27(23) (2006) 4192–4203. [10] D. Lakstein, W. Kopelovitch, Z. Barkay, M. Bahaa, D. Hendel and N. Eliaz, Enhanced osseointegration of grit-blasted, NaOH-treated and electrochemically hydroxyapatite-coated Ti-6Al-4V implants in rabbits, Acta Biomater. 5 (2009) 2258–2269.
P-3 Flexor Tendon Injury, Repair, and Rehabilitation – A Good Model For Studying Connective Tissue Healing and Remodeling C. Zhao, Y.-L. Sun, S.L. Moran, P.C. Amadio, K.-N. An. Mayo Clinic, Rochester MN, USA In the last few decades, our understanding of connective tissues healing and remodeling has been advancing rapidly due to the development of modern cellular and molecular biology. This has led to greatly improved clinical outcomes for the treatment of musculoskeletal connective tissue injuries, such as fractures, and tendon and ligament injuries. However, orthopedic surgeons are still challenged by some clinical problems or complications which are associated with healing and remodeling, such as spinal osteoporosis, fracture non-union, tendinopathy, and tendon and ligament injuries. The history of wound care traces back to prehistory when the hunter-gatherer used herbal medicine to speed up wound healing. In 1500 BC, the Ebers Papyrus, a preserved medical document from ancient Egypt, described the use of lint for wound closure, animal grease for a barrier from environmental pathogens, and honey for an antibiotic agent, all of which are basic principles for caring for wounds today. All connective tissues in the human body follow a similar pathway to healing, including three sequential, yet overlapping, phases, i.e. inflammation, proliferation, and remodeling, Healing can also be classified as intrinsic or extrinsic, based on the healing resources. The healing status can also be either contact healing or gap healing. All of these healing parameters have to be balanced appropriately to achieve the best outcome. Our research interests are flexor tendon injuries, one of the most challenging clinical problems. As a representative example of connective tissue healing, I will focus on healing and remodeling after flexor tendon injuries. The mechanism of flexor tendon healing has been a popular clinical and research topic for nearly a century. In the early 20th century, the founding father of hand surgery in the US, Dr. Sterling Bunnell, used the term “No Man’s Land” to describe the region where the flexor tendons passed through the digital sheath. This theory guided clinical practice for over half a century, that primary repair of a lacerated flexor tendon in No Man’s Land should be discouraged due to severe adhesion formation and repaired tendon ruptures. Therefore, secondary tendon grafting was considered as the alternative treatment. In the middle of the 20 century, many hand surgeons reported encouraging outcomes of primary repair of flexor tendons. After several decades of debate, primary repair has been generally accepted as the standard treatment following flexor tendon injury. However, flexor tendon healing and remodeling still remains a clinical and research challenge due to high complication rates. Tendon experiences the three phase healing process. In the first inflammatory phase, the blood supply is the key for delivering inflammatory cells and growth factors. Neutrophils with monocytes
Contents lists available at ScienceDirect
Journal of Biomechanics journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com
Plenary Lectures P-1 Hip Resurfacing: The Past, the Present and the Future A. Moroni. Bologna University, Rizzoli Orthopaedic Institute, Italy 1951 saw the first hip resurfacing (HR) procedure performed by Sir John Charnley using teflon-on-teflon bearings [1]. Approximately 20 years later, a polyethylene acetabular component and metal femoral component had become popular but osteolysis was prevalent due to tissue response to wear particles [2,3]. By the early 1980s, HR had almost been phased out due to high failure rates, but work continued in some centres, leading to the development of metal-on-metal (MOM) HR prostheses. The advantages of using MOM components in HR include less wear and bone re-absorption, and a low rate of dislocation [4]. Indeed, various reports in the literature have documented excellent short and mid-term results and low complication rates associated with MOM HR [5–7]. The results of our series of over 1000 patients treated with MOM HR are in agreement with such reports. The mean patient age at the time of surgery was 53.8 years (range 16 to 82). The mean Harris hip score (HHS) was 98 points at a mean follow-up of 2 years. The following major complications were recorded: 9 femoral neck fractures (FNFs), 2 acetabular component loosenings, 1 pseudotumour and 1 sciatic peroneal nerve deficit. Although we believe that MOM HR is a successful technique, long-term studies have not yet been published and there is always room for improvement. MOM implants do in fact have several drawbacks, including osteolysis, implant loosening, the development of hypersensitivity and pseudotumours [8–10], and serum metal ion elevation [11], the latter being particularly important with regards to fertile females. A novel type of bearing for use in HR consists of an uncemented 2.7 mm-thick acetabular polycarbonate-urethane (PCU) component, which can be coupled to large diameter metal heads. Commercially known as the Tribofit® Acetabular Buffer™ (Active Implants Corporation, Memphis Tennessee, USA), this innovative bearing allows fluid film lubrication and as a result, wear is minimized. PCU is a hydrophilic, biocompatible, endotoxin-resistant material and acts as a stress-absorber, transmitting loads to the subchondral bone in a physiological manner. As of January 2010, 3 patients with avascular necrosis (AVN) and 5 with osteoarthritis (OA) were treated with HR using the Buffer™. Large diameter cobalt-chromium (CoCr) resurfacing heads were used in all patients (Tribofit® , Active Implants Corporation, Memphis, Tennessee, USA). The mean patient age at the time of surgery was 53.1 years (range 30 to 68). In pristine sockets, no acetabular bone reaming was performed and the Buffer™ alone was used. In 3 of the OA patients who had deformed sockets, standard reaming was performed and the Buffer™ was placed into an acetabular metal shell, the former acting as a liner. The mean follow-up in this patient series was 12 months (range 0 to 25). No osteolysis or loosening were observed on X-rays. However, in 1 patient who did not have the acetabular metal shell, the acetabular bone had been mistakenly reamed. The patient became symptomatic 2 years after surgery and periacetabular bone 0021-9290/$ – see front matter © 2010 Elsevier Ltd. All rights reserved.
rarefaction was visible. The mean HHS of the remaining cases at the latest follow-up was 99. In conclusion, HR has gone a long way since its development over 50 years ago. MOM HR is a successful technique performed worldwide, but implant longevity and the long-term effects of wear debris remain unclear. However, with the continuous evolution of hip bearings and the recent developments in technology, HR is set to be taken to the next level. Reference(s) [1] Charnley JC. Arthroplasty of the hip: a new operation. Lancet I, 1961; 1129–1132. [2] Amstutz HC, Graff-Radford A, Gruen TA, Clarke IC. THARIES surface replacements: a review of the first 100 cases. Clin Orthop Relat Res. 1978; 134:87–101. [3] Howie DW, Campbell D, McGee M, Cornish BL. Wagner resurfacing hip arthroplasty. The results of one hundred consecutive arthroplasties after eight to ten years. J Bone Joint Surg Am. 1990; 72(5):708–714. [4] K.A. De Smet, C. Pattyn, R. Verdonck. Early results of primary Birmingham hip resurfacing using a hybrid metal-on-metal couple. Ghent University Hospital, Ghent, Belgium. Hip International 2002; 12(2):158–162. [5] Daniel J, Pynsent PB, McMinn DJ. Metal-on-metal resurfacing of the hip in patients under the age of 55 years with osteoarthritis. J Bone Joint Surg Br. 2004; 86(2):177–184. [6] Treacy RB, McBryde CW, Pynsent PB. Birmingham hip resurfacing arthroplasty. A minimum follow-up of five years. J Bone Joint Surg Br. 2005; 87(2):167–170. [7] Amstutz HC, Beaule´ PE, Dorey FJ, Le Duff MJ, Campbell PA, Gruen TA. Metal-on-metal hybrid surface arthroplasty: two to six-year follow-up study. J Bone Joint Surg Am. 2004; 86-A(1):28–39. [8] Park Y-S, Moon Y-W, Lim S-J, Yang J-M, Ahn G, Choi Y-L. Early osteolysis following second-generation metal-on-metal hip replacement. J Bone Joint Surg Am. 2005; 87:1515–1521. [9] Willert H-G, Buchhorn GH, Fayyazi A, Flury R, Windler M, Koster G, Lohmann CH. Metal-on-metal bearings and hypersensitivity in patients with artificial hip joints. A clinical and histomorphological study. J Bone Joint Surg Am. 2005; 87:28–36. [10] Pandit H, Glyn-Jones S, McLardy-Smith P, Gundle R, Whitwell D, Gibbons CL, Ostlere S, Athanasou N, Gill HS, Murray DW. Pseudotumours associated with metal-on-metal hip resurfacings. J Bone Joint Surg Br. 2008; 90(7):847–851. [11] Clarke MT, Lee PTH, Arora A, Villar RN. Levels of metal ions after small and large diameter metal-on-metal hip arthroplasty. JBJS 2003; 85B6:913–917.
P-2 Electrocrystallization of Calcium Phosphates for Orthopaedic Implants N. Eliaz. Tel-Aviv University, Israel Apatite is the primary inorganic constituent of all mammalian skeletal and dental tissues. It belongs to the family of calcium phosphates (CaP), which includes, among others, hydroxyapatite (HAp, Ca5 (PO4 )3 (OH)) and octacalcium phosphate (OCP, Ca4 (HPO4 )(PO4 )2 ·2.5H2 O). In their synthetic form, apatites are typically bioactive ceramics, which are more osteoconductive than
S4
Plenary Lectures / Journal of Biomechanics 43S1 (2010) S3–S14
metal surfaces and form direct bonds with adjacent hard tissues via dissolution and ion exchange with body fluids. Hence, several types of synthetic apatites are now commercially available for use in bone repair, bone augmentation, bone substitution, and as coatings on orthopaedic and dental implants. Several methods have been explored to deposit CaP coatings in order to enhance implant fixation. Plasma spraying is the most common technology used commercially. Since the early 1990’s, however, much interest in electrodeposition has evolved. In recent years, our group has been studying different aspects related to electrocrystallization (i.e. the nucleation and crystal growth in electrochemical systems under the influence of an electric field) of HAp and other calcium phosphates. Some of these aspects will be presented in this talk. Electrocrystallization was achieved potentiostatically in solutions containing calcium nitrate and ammonium dihydrogen phosphate at an initial pH of either 4.2 (HAp4.2) or 6.0 (HAp6.0). Both the surface texture and the contact angle of the ground titanium substrate changed as a result of either heat treatment following soaking in NaOH solution or soaking in H2 O2 solution [1,2]. Consequently, the shape of the current transients during potentiostatic deposition of HAp changed, and the resulting coatings exhibited different surface textures and contact angles. Pure, highly crystalline HAp could be deposited on CP-Ti and Ti-6Al-4V [3–6]. The HAp4.2 coatings were thicker, less crystallized and more porous than HAp6.0 coatings, and revealed traces of OCP as well as a different surface morphology [5]. Bath temperature played an important role in the formation of the stoichiometric HAp coating. The synthetic HAp exhibited a hetero-epitaxial-like behaviour on Ti substrates, similar to the biological apatite [7]. The deposition changed from instantaneous nucleation/2D growth to progressive nucleation/3D growth [7,8]. The corrosion resistance of HAp6.0 coatings was better than that of HAp4.2 coatings [5]. The solubility of the CaP affected the kinetics of bone ingrowth significantly [9]. The use of Ra and Z rms might lead to misleading conclusions, particularly when studying porous coatings such as HAp. The use of the S dr was found more sensitive and reliable in distinguishing between different surfaces and predicting their effect on cell attachment [1]. The higher content of OCP in NaOH-ED-HAp, as evident from X-ray photoelectron spectroscopy (XPS) analysis of the oxygen shake-up peaks, and the associated increase in the solubility of this coating in vivo may be responsible for the enhanced osseointegration [8,10]. Evaluation of the shape and coverage of MBA-15 cells in vitro showed that the HAp6.0 coatings provided enhanced cell response [1]. It is concluded that electrochemical deposition of HAp following soaking in NaOH may become attractive, both industrially and clinically, for coating cementless implants used for joint reconstruction. Reference(s) [1] N. Eliaz, S. Shmueli, I. Shur, D. Benayahu, D. Aronov and G. Rosenman, The effect of surface treatment on the surface texture and contact angle of electrochemically deposited hydroxyapatite coating and on its interaction with bone-forming cells, Acta Biomater. 5 (2009) 3178– 3191. [2] O. Ritman, The effect of surface treatments on the interaction of HAp-coated titanium with cells and bacteria, M.Sc. Thesis, Tel-Aviv University, Israel (2008). [3] T.M. Sridhar, N. Eliaz, U. Kamachi Mudali and Baldev Raj, Electrophoretic deposition of hydroxyapatite coatings and corrosion aspects of metallic implants, Corros. Rev. 20(4–5) (2002) 255–293. [4] N. Eliaz, T.M. Sridhar, U. Kamachi Mudali and Baldev Raj, Electrochemical and electrophoretic deposition of hydroxyapatite for orthopaedic applications, Surf. Eng. 21(3) (2005) 238–242. [5] N. Eliaz and T.M. Sridhar, Electrocrystallization of hydroxyapatite and its dependence on solution conditions, Cryst. Growth Des. 8(11) (2008) 3965–3977. [6] N. Eliaz, Electrocrystallization of calcium phosphates, Israel J. Chem. 48(3/4) (2008) 159–168.
[7] N. Eliaz and M. Eliyahu, Electrochemical processes of nucleation and growth of hydroxyapatite on titanium supported by real-time electrochemical atomic force microscopy, J. Biomed. Mater. Res. A 80(3) (2007) 621–634. [8] N. Eliaz, W. Kopelovitch, L. Burstein, E. Kobayashi and T. Hanawa, Electrochemical processes of nucleation and growth of calcium phosphate on titanium supported by real-time quartz crystal microbalance measurements and XPS analysis, J. Biomed. Mater. Res. A 89(1) (2009) 270–280. [9] H. Wang, N. Eliaz, Z. Xiang, H.-P. Hsu, M. Spector and L.W. Hobbs, Early bone apposition in vivo on plasma-sprayed and electrochemically deposited hydroxyapatite coatings on titanium alloy, Biomaterials 27(23) (2006) 4192–4203. [10] D. Lakstein, W. Kopelovitch, Z. Barkay, M. Bahaa, D. Hendel and N. Eliaz, Enhanced osseointegration of grit-blasted, NaOH-treated and electrochemically hydroxyapatite-coated Ti-6Al-4V implants in rabbits, Acta Biomater. 5 (2009) 2258–2269.
P-3 Flexor Tendon Injury, Repair, and Rehabilitation – A Good Model For Studying Connective Tissue Healing and Remodeling C. Zhao, Y.-L. Sun, S.L. Moran, P.C. Amadio, K.-N. An. Mayo Clinic, Rochester MN, USA In the last few decades, our understanding of connective tissues healing and remodeling has been advancing rapidly due to the development of modern cellular and molecular biology. This has led to greatly improved clinical outcomes for the treatment of musculoskeletal connective tissue injuries, such as fractures, and tendon and ligament injuries. However, orthopedic surgeons are still challenged by some clinical problems or complications which are associated with healing and remodeling, such as spinal osteoporosis, fracture non-union, tendinopathy, and tendon and ligament injuries. The history of wound care traces back to prehistory when the hunter-gatherer used herbal medicine to speed up wound healing. In 1500 BC, the Ebers Papyrus, a preserved medical document from ancient Egypt, described the use of lint for wound closure, animal grease for a barrier from environmental pathogens, and honey for an antibiotic agent, all of which are basic principles for caring for wounds today. All connective tissues in the human body follow a similar pathway to healing, including three sequential, yet overlapping, phases, i.e. inflammation, proliferation, and remodeling, Healing can also be classified as intrinsic or extrinsic, based on the healing resources. The healing status can also be either contact healing or gap healing. All of these healing parameters have to be balanced appropriately to achieve the best outcome. Our research interests are flexor tendon injuries, one of the most challenging clinical problems. As a representative example of connective tissue healing, I will focus on healing and remodeling after flexor tendon injuries. The mechanism of flexor tendon healing has been a popular clinical and research topic for nearly a century. In the early 20th century, the founding father of hand surgery in the US, Dr. Sterling Bunnell, used the term “No Man’s Land” to describe the region where the flexor tendons passed through the digital sheath. This theory guided clinical practice for over half a century, that primary repair of a lacerated flexor tendon in No Man’s Land should be discouraged due to severe adhesion formation and repaired tendon ruptures. Therefore, secondary tendon grafting was considered as the alternative treatment. In the middle of the 20 century, many hand surgeons reported encouraging outcomes of primary repair of flexor tendons. After several decades of debate, primary repair has been generally accepted as the standard treatment following flexor tendon injury. However, flexor tendon healing and remodeling still remains a clinical and research challenge due to high complication rates. Tendon experiences the three phase healing process. In the first inflammatory phase, the blood supply is the key for delivering inflammatory cells and growth factors. Neutrophils with monocytes